How to Unsuspend WHM operation

We are trying to delete some of the websites from our server and keep getting the following error message.

Error: The / partition on this server is running out of disk space. WHM operation has been temporarily suspended to prevent something bad from happening. Please ask your system admin to remove any files not in use on that partition.

Well, if you can ssh into the box, you could manually clear out some of the folders (mail, for instance) on the accounts you're going to delete... as well as remove any backups that aren't needed, log files, etc.